The present disclosure is directed to enhancing Electro-Magnetic Compatibility (EMC) robustness of a 3-wire sensor output signal. Class A functionality on the output is ensured when the Integrated Circuit (IC) is exposed to either conducted or coupled pulses on the supply (e.g., Direct Capacitive Coupling (DCC)), inductive transients (e.g., Radio frequency Immunity (RI 130)), or short supply drops below a reset level.
One approach for enhancing EMC robustness uses an external storage capacitor, which supplies the IC during EMC pulses. A drawback of this approach is that it requires an extra bond pad and external passive component.
Another approach uses a relatively large integrated capacitor to supply output circuitry. Power management loss circuitry detects a supply voltage drop and outputs a hold signal to control the logic circuitry. During a power loss, the capacitor is decoupled from the supply line using a diode/switch, and a voltage stored on the capacitor supplies the output circuitry. A drawback of this approach is that it requires a relatively large integrated capacitor to supply all of the output circuitry. This drawback becomes even more significant at higher temperatures when additional leakage leads to a relatively quick loss of the stored voltage, which determines a significant drift of output sensor parameters, such as the output voltage saturation. Additionally, using a large capacitor to ensure good behavior at high temperatures results in slow discharging of the capacitor at lower temperatures when the power is switched off.